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| 型号： | MAX1904EAI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/33页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PWR SPLY LN 28-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 4.2 V ~ 30 V |
| 输出数： | 4 |
| 输出电压： | 2.5 V ~ 5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
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500kHz Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
Table 5. Low-Voltage Troubleshooting Chart
SYMPTOM
Sag or droop in V OUT
under step-load change
Dropout voltage is too
high (V OUT follows V IN as
V IN decreases)
Unstable — jitters between
different duty factors and
frequencies
Secondary output won ’ t
support a load
Poor efficiency
Won ’ t start under load or
quits before battery is
completely dead
CONDITION
Low V IN - V OUT
differential, <1.5V
Low V IN - V OUT
differential, <1V
Low V IN - V OUT
differential, <0.5V
Low V IN - V OUT
differential,
V IN < 1.3 ?
V OUT(MAIN)
Low input voltage,
<5V
Low input voltage,
<4.5V
ROOT CAUSE
Limited inductor-current slew rate
per cycle.
Maximum duty-cycle limits
exceeded.
Normal function of internal low-
dropout circuitry.
Not enough duty cycle left to
initiate forward-mode operation.
Small AC current in primary can ’ t
store energy for flyback
operation.
V L linear regulator is going into
dropout and isn ’ t providing good
gate-drive levels.
V L output is so low that it hits the
V L UVLO threshold.
SOLUTION
Increase bulk output capacitance per
formula (see the Low-Voltage Operation
section). Reduce inductor value.
Reduce operation to 333kHz. Reduce
MOSFET on-resistance and coil DCR.
Increase the minimum input voltage or
ignore.
Reduce operation to 333kHz. Reduce
secondary impedances; use a Schottky
diode, if possible. Stack secondary
winding on the main output.
Use a small 20mA Schottky diode for
boost diode. Supply V L from an external
source.
Supply V L from an external source other
than V IN , such as the system 5V supply.
P ( tran ) = V IN × I LOAD ×
where t D is the diode-conduction time (120ns typ) and
V FWD is the forward voltage of the diode.
f ×
3
2
×
[ ( V IN × C RSS / I GATE ) - 20 ns ]
This power is dissipated in the MOSFET body diode if
where C RSS is the reverse transfer capacitance of the
high-side MOSFET (a data sheet parameter), I GATE is
the DH gate-driver peak output current (1.5A typical),
and 20ns is the rise/fall time of the DH driver (20ns typ).
P(gate) = Q G ? f ? V L
where V L is the internal-logic-supply voltage (5V), and
Q G is the sum of the gate-charge values for low-side
and high-side switches. For matched MOSFETs, Q G is
twice the data sheet value of an individual MOSFET. If
V OUT is set to less than 4.5V, replace V L in this equa-
tion with V BATT . In this case, efficiency can be
improved by connecting V L to an efficient 5V source,
such as the system 5V supply:
P(diode) = I LOAD ? V FWD ? t D ? f
no external Schottky diode is used:
P(cap) = (I RMS ) 2 x R ESR
where I RMS is the input ripple current as calculated in the
Design Procedure and Input-Capacitor Value sections.
Light-Load Efficiency Considerations
Under light loads, the PWM operates in discontinuous
mode, where the inductor current discharges to zero at
some point during the switching cycle. This makes the
inductor current ’ s AC component high compared to the
load current, which increases core losses and I 2 R loss-
es in the output filter capacitors. For best light-load effi-
ciency, use MOSFETs with moderate gate-charge
levels, and use ferrite, MPP, or other low-loss core
material.
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| MAX1904EAI-TG074 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1904ETJ | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1904ETJ+ | 功能描述:DC/DC 开关控制器 500kHz Multi-Output Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1904ETJ+T | 功能描述:DC/DC 开关控制器 500kHz Multi-Output Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1904ETJ-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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